In many applications, two-motor or multiple-motor drives are used for hydrostatic drives where a broad range of rotational speeds is required combined with large torque ranges, whereby the power available is limited. Such broad spectrums of rotational speed and torque, also referred to as conversion ranges, are also expected to be available in highly diverse operating situations with minimum control/regulation effort on a load-dependent basis and/or depending on the operating situation. For example, a high torque is required in hydrostatic motor vehicle drives for the purpose of acceleration from standing or for hill climbs, but this torque decreases as travel speed increases. In order to reach as high a travel speed as possible, high rotational speeds are required at the output shaft of a hydrostatic drive. Such high demands of the conversion or transmission range—on the one hand a high level of torque and on the other hand a high rotational speed—are often not possible to achieve in a satisfactory manner with a single hydraulic motor in the hydrostatic drive. What is more, the market calls for increasingly high maximum rotational speeds or travel speeds which extend the transmission range of a hydrostatic drive. In the state of the art, this is addressed by means of so-called multiple-motor drives, whereby for example two or more motors are provided to supply initially a high torque in order to accelerate from standing, and whereby the number of driving hydraulic motors is reduced as travel speed is increased, until for example often only one hydraulic motor remains in the drive until maximum speed is reached.
In this type of hydrostatic drive usually comprising two motors, the hydraulic motor for the provision of high torque, which is hydraulically connectable and disconnectable, is preferably selected as being larger in its maximum stroke volume than the hydraulic motor operating permanently in the drivetrain. The reason for this generally lies in the fact that a hydraulic motor with a small maximum displacement can reach a higher rotational speed but the level of maximum torque it can provide is lower, in accordance with the relatively small maximum displacement. Both radial piston motors and axial piston motors are used in this type of two-motor or multiple-motor drive.